Approximately 65,000 intermodal rail car cars are used in the United States. Intermodal rail cars are specifically designed to transport both domestic and International Standards Organization (ISO) containers. ISO containers are eight feet wide, and either eight feet six inches tall or nine feet six inches tall, and are typically either 20 or 40 feet long, although larger sizes are available. 20-foot long ISO containers have a gross weight (lading and tare) load limit of 67,200 pounds. Intermodal rail cars may be loaded with two tiers of containers. With ISO containers, the lower tier generally consists of either two 20-foot ISO containers positioned end-to-end in the rail car or one 40-foot container, and the upper tier generally consists of one 40-foot ISO container stacked on top of either the two 20-foot ISO containers or the single 40-foot container.
The average intermodal rail car is between 10-12 years old and, as a result of overstress created by fully loaded 20-foot containers, many of the intermodal rail cars have become structurally compromised. In particular, the central portion of the intermodal rail car potentially becomes stressed to the point of failure of the supporting horizontal steel structure. As a result of this stress caused by the fully loaded 20-foot containers, the Association of American Railroads (AAR) reduced the maximum allowable weight limit for 20-foot ISO containers from 67,200 pounds to 52,900 pounds effective January 2012, thereby decreasing transportation efficiency of the US intermodal rail industry. This invention will restore the ability of the current intermodal rail fleet to again carry fully loaded 20-foot containers without damaging the rail cars.